The IEEE 802.11ac “beam-forming” standard will change the way we connect to Wi-Fi, says Matthew Gast
Next year, an update to Wi-Fi standards will reach products, letting routers and access points create directional “beams” of data to each device that connects to them – effectively changing the devices from “hubs” to “switches”.
The new beam-forming feature is the most interesting part of the latest faster version of the Wi-Fi standards, IEEE 802.11 ac, which is starting to find its way into products now. It will hit full speed next year, according to Matthew Gast, product manager at Aerohive networks, author of a shelf of O’Reilly books on Wi-Fi and a long-time contributor to the IEEE standards committees which specify Wi-Fi’s underlying definitions.
A new look for Wi-Fi
The new version of Wi-Fi is coming in quickly and peacefully, without the vendor struggles that accompanied the last generation, 802.11n. The Wi-Fi Alliance, which handles branding, has begun to approve 802.11ac products like those announced by vendors Aruba and Cisco.
Vendors fought over 802.11n because it introduced new technology, MIMO (multiple input multiple output) , which opened multiple channels between the access point and clients such as laptops and phones, and it handled both sections of Wi-Fi spectrum, 2.4GHz and 5GHz, which had previously had separate standards.
Although the Alliance is pulling out the stops and branding this as “5G”, most of the changes in 802.11ac are fairly straightforward, Gast told TechWeekEurope on a visit to London. The beam-forming part of the standard will be hardest to implement, and won’t arrive till the “second wave” of 802.11ac products, which should be next year.
This year’s 802.11ac access points will give a faster speed – as long as your phone or laptop supports 802.11ac (look for a Wi-Fi Alliance “5G” sticker). The speed increase comes by a couple of different means, Gast told us.
Alien face hugger
Firstly, the number of spatial channels are increased. Today’s 802.11n routers can send three streams of data simultaneously, by using radio reflections and so forth. The new standard will allow up to eight streams – but Gast doesn’t think the feature will get used much at first: “To have eight streams, your phone would have to have eight antennas, and look like an alien face-hugger”.
Multiple streams will be used more in wireless network links between routers for jobs like mesh networks.
Secondly, 802.11ac allows wider data channels, going up from 802.11n’s option of 20MHz or 40MHz channels, by allowing 80MHz or 160MHz channels, which can carry twice or four times as much data as a 40MHz channel, roughly speaking.
Wi-Fi networks work by grabbing a channel that is not used at that particular location and , as it turns out, even in the comparatively empty 5Ghz band, it’s hard to set up a 160MHz channel, but 80MHz of unoccupied space is easier to get, so faster connections should be possible.
A third improvement is moving from an upper limit of 64QAM encoding to 256QAM. This means that 802.11ac devices, given a good signal strength, can try to resolve a greater range of phases and amplitudes giving a greater throughput. Going from 64QAM to 256QAM takes your signal from 6 bits to 8 bits, and increases the throughput by 30 percent – as long as you have an extra 5dB of gain, Gast explained.
All in all, these changes will give you some throughput improvement, for a price premium which looks like being about 30 percent on top of today’s access point prices, said Gast.
The 802.11ac standard is available in some consumer devices, and will be available in business grade machines this year – and since all are based on silicon from Broadcom or Atheros, their performance should be similar to each other.
It’s next year that things get interesting, as the beam-forming standard arrives. Effectively, this gives every device its own connection to the Wi-Fi network, so they are no longer sharing time-slices with other devices. Gast says Wi-Fi is then effectively a “switched” network – and this upgrade is something like the change that happened when Ethernet devices changed from being hubs to switches, and everyone got 100Mbps (or 1Gbps) of their own.
Beam-forming in itself is not new. There have been multiple ways to do it within the hard-fought 802.11n standard. Vendors (including Ruckus) have argued over who does it best. In the 802.11ac standard, the IEEE banged some heads together and created one standard for the technology: “This time the IEEE issued a specification requirements document,” he told us.
The beam-forming technology will be popularised as “multi-user MIMO” because it handles multiple devices differently, he explained. It should increase the reliability and throughput of Wi-Fi yet again.
Overall, it’s another boost to the political strength of Wi-Fi, which now has the ears of regulators to such an extent that America’s FTC regulator makes it a priority to offer any newly-released spectrum for the use of technologies like Wi-Fi. Because Wi-Fi is an unlicensed system, which can share any spectrum with other technologies without blocking them, it can be fitted into regimes for spectrum available under White Space regimes.
The 802.11ac standard has been described as “Gigabit Wi-Fi” because it increases the theoretical speed of Wi-Fi from today’s top level of 450Mbps, up to Gigabit speeds. Those top speeds have always been notoriously optimistic, brought back to earth by the effects of time-sharing and interference.
Yet the move to “switched” Wi-Fi through beam-forming will be far more significant than a speed increase, as it should go some way to removing those uncertainties.
Are you acquainted with Wi-Fi ? Try our quiz!